WSMP software connects to League of Memories central server and runs GameServer instances.
WSMP doesn't manage lobbies and only runs GameServer instances. So it connects to the LoM central server to retrieve all the info in order to start the game. You can run it without a Key but your server will run as unverified. In order to run a verified server you need a key, which are distributed to servers that have been running for some time and guarantee that they are able to run a full game without issues.